RFR(XS): 8001424: G1: Rename certain G1-specific flags

[John Cuthbertson]

Hi Everyone,

Some flag name changes suggested by the JVM performance team based upon 
feedback they have received. The webrev can found at: 
http://cr.openjdk.java.net/~johnc/8001424/webrev.0/

Basically the changes are those listed in the webrev:

G1DefaultMinNewGenPercent is being replaced by G1NewSizePercent
G1DefaultMaxNewGenPercent is being replaced by G1MaxNewSizePercent
G1OldCSetRegionLiveThresholdPercent is being replaced by 
G1MixedGCLiveThresholdPercent

Thanks,

JohnC